Clues to otherworldly planet formation have so far involved holes and rings in various dust disks, along with some clumps of material. But these features have been spotted at great distances from stars, and theorists have found other explanations for them.
The new Keck observations reveal an odd-orbiting batch of dust at a distance roughly equal to Jupiter's path around the Sun.
"No obvious explanation exists for its origin other than the gravitational influence of planets," said David Koerner of the University of Pennsylvania, who led one of the studies along with graduate student Zahed Wahhaj.
The researchers spotted a batch of dust orbiting in the opposite direction from a larger batch of material previously spotted by the Hubble Space Telescope. The newly detected feature is also inclined 14 degrees to the plane of the main dust disk.
"The different inclinations of dust grain orbits around Beta Pic bear a resemblance to those of planetary orbits in our own solar system." Koerner said. "Plutos orbit is inclined by 17 degrees compared to Earths, and Mercurys differs by 7 degrees, for example. The new Keck images may be interpreted as circumstantial evidence for a similarly organized planetary system."
Nearly 100 planets have been detected outside our solar system, but most are larger than Jupiter. No solar systems like our own have ever been found. Yet most astronomers expect to find some once technology improves. Meanwhile, observations of dust around young stars provides potential clues about the formation of our own solar system.
Separate observations of Beta Pictoris were led by Alycia Weinberger, now at the Carnegie Institution of Washington. Weinberger's team analyzed the newly spotted feature and found it is made of small silicate particles that are hotter than expected.
"It may be that as a planet warps the disk, it also causes more collisions of rocks in its neighborhood," Weinberger said.
Small dust grains produced by collisions would be hotter than larger dust grains. Collisions of rocks and boulders are thought to be an important step in the early construction of a planet.
Both teams will present their discoveries today at the Gillett Symposium on "Debris Disks and the Formation of Planets" in Tucson, Arizona.
Detailed views of dust disks can only be made in infrared wavelengths, which reveal heat emissions rather than visible light. Only in recent years have ground-based telescopes developed the ability to make these sensitive detections. The Beta Pictoris observations were made using both telescopes at the W.M. Keck Observatory. Each has a 400-inch (10-meter) aperture, the largest in the world.
Beta Pictoris is a young star, about 20 million years old, and is about 63 light-years away.
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